The study of the transcription of the rRNA gene from Tetrahymena pyriformis and the processing of the precursor ribosomal RNA molecule, both in vivo and in vitro, will be continued. The 5 feet and 3 feet termini containing oligonucleotides of the precursor rRNA molecule, pulse labeled in vivo will be isolated and their base sequences determined. These sequences, which originate at the sites of initiation and termination, in vivo will give us an unambiguous assay for the specificity of transcription initiation and termination in vitro. The products of the various cleavage processing events in vivo will be isolated, their 5 feet and 3 feet containing oligonucleotides will be isolated and the base sequences of these terminal oligonucleotides will be determined. These sequences will both yield some evidence of the sequence relatedness of the various processing events, and will serve as a measure of the specificity of processing cleavages carried out in vitro. Finally, the RNA which is synthesized in isolated macronuclei by an alpha amanitin resistent enzyme will be characterized and its relation to the 25S and 17S rRNA will be determined by (1) hybridization to rRNA, (2) hybridization competition with pure 25S and 17S rRNA and (3) by a comparison of the T1 and pancreatic RNAse fingerprints of the in vitro synthesized RNA with the 25S and 17S rRNA.